Adding Cypress for e2e testing (#85)

* using the higher-level react-testing-library, and regenerating snapshot - renders real DOM elements
* Basic e2e testing with Cypress, following the guide here: https://www.gatsbyjs.com/docs/how-to/testing/end-to-end-testing/ ; needed to install cypress-local to avoid jest-cypress collision
* Adding accessibility testing support and basic a11y tests
* adding failure logging
* Adding nightly test run
* Fix misc stuff from lighthouse (#81)
* Removing local-cypress, relying instead on a combination
of type reference and eslint-plugin-cypress;
adding cypress to jest ignore paths to avoid conflict -
`npm test` is now jest-only, use `npm run test:e2e` to run cypress tests
* updating comment to clarify timezone

client/cypress/e2e/accessibility.test.js

@@ -0,0 +1,34 @@
+// / <reference types="Cypress" />
+
+// Define at the top of the spec file or just import it
+
+// eslint-disable-next-line require-jsdoc
+function terminalLog(violations) {
+  cy.task(
+      'log',
+      `${violations.length} accessibility violation${
+        violations.length === 1 ? '' : 's'
+      } ${violations.length === 1 ? 'was' : 'were'} detected`,
+  );
+  // pluck specific keys to keep the table readable
+  const violationData = violations.map(
+      ({id, impact, description, nodes}) => ({
+        id,
+        impact,
+        description,
+        nodes: nodes.length,
+      }),
+  );
+
+  cy.task('table', violationData);
+}
+
+
+describe('Accessibility tests', () => {
+  beforeEach(() => {
+    cy.visit('/').get('main').injectAxe();
+  });
+  it('Has no detectable accessibility violations on load', () => {
+    cy.checkA11y(null, null, terminalLog);
+  });
+});